The present invention relates to a drive for a machine of a type having a short-stroke motor and a pulse-decoupling device for decoupling pulses of the short-stroke motor from the machine using closed-loop control.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Workpieces or tools are moved using many machines in industrial production processes. The movement is performed along fixedly predetermined axle paths. The operating speed of the machine is substantially dependent on the speed of the delivery and transport movements. In the sense of high levels of machine productivity, therefore, high axle speeds are therefore desired.
In most cases, the delivery movements, which require a certain degree of precision, are implemented by electrical servo drives which are subject to closed-loop control. If a direct drive is not used, the torque of the servomotor is transmitted to the machine carriages, which, intended to be moved linearly are with the aid of transmission elements, such as ball screw spindles, toothed belts or toothed racks, for example. Such drive systems are widespread in industrial technology.
High speeds of the linear movements are necessarily accompanied by high acceleration levels and a high degree of jerkiness (change in the acceleration per unit time). In particular, the degree of jerkiness increases dramatically with the operating speed of the servo axle. The jerkiness causes the machine structure to oscillate, and this can have a disadvantageous effect on the precision and contour accuracy of the manufacturing process. It is then often necessary to scale back the acceleration and the axle speed to such an extent that the critical jerkiness values are not exceeded. The limitation of the axle speed has a negative effect on the productivity of the machine, however. It would therefore be desirable to be able to increase the axle speed without thus exciting oscillations in the machine.
Forward-feed axles for short-stroke movements with very high dynamics (order of magnitude of accelerations: 30 g; order of magnitude of frequencies: 100 Hz), are usually in the form of linear motors with moving secondary parts (magnets). In order to keep the mass which is moved low, the secondary part with the magnets is just long enough for the coils of the primary part to always be completely covered.
It is often necessary to vary the working point of a short-stroke (linear) motor at which the short-stroke motor performs its movements. This is not possible owing to the above-described boundary conditions (secondary part which is as short as possible) with the displacement path of the short-stroke motor.
In order to adjust the working point, until now it has therefore been necessary to install the complete, pulse-decoupled unit on an additional auxiliary positioning axle, which takes on the relatively large displacement paths. This axle can become jammed during operation.
It would therefore be desirable and advantageous to address prior art shortcomings and to enable implementation of a working-point adjustment of the short-stroke motor in a simple and yet reliable manner.